Not Applicable
Not Applicable
Not Applicable
1. Technical Field
The field of the present invention is electronic test instrumentation. More particularly, the field relates to a card based switch system for use in a C sized VXI electronic test system.
2. Background Art
Automated test systems are used to help manufacturers improve production quality and throughput. These automated test systems comprise multiple electronic test instruments such as voltmeters, power supplies and digital scopes. By automating the testing process, a manufacturer is able to more accurately and more efficiently test products for compliance with internal specifications and customer requirements. Traditionally, automated test equipment systems have been built using instrumentation which fits into a 19 inch wide rack system. Such systems were bulky, heavy and difficult to interconnect. Interconnection was not only physically a problem but limited the speed at which the entire system could operate, thus degrading test system throughput.
In response for the need for a more compact and more efficient automated test system, the automated test system industry developed a standard now commonly referred to as the xe2x80x9cVXIxe2x80x9d standard. VXI defines the physical and electrical interconnection between automated test equipment from manufacturers complying with the standard. With VXI a test system integrator chooses a VXI chassis and then selects VXI card based instrumentation specific to the test requirements.
The VXI chassis has a frame containing multiple slots. Each slot is configured to receive an instrumentation card. A card taking up one slot is referred to as a single slot VXI instrument. To use the instrument, the instrument card is slid into one of the slots of the VXI chassis until connectors on the back of the card couple with a VXI backplane on the back of the VXI chassis. The VXI backplane is a high speed communication bus which not only provides power for the VXI instrument card but allows instruments within a chassis to communicate and allows interconnection between multiple VXI chassis.
Although many test instruments are available in the single slot VXI configuration, several instruments are too complex and require a larger card frame. For such complex instruments, the VXI standard allows an instrument card to take up multiple slots. For example, a VXI instrument card taking up two slots is referred to as a double slot VXI card.
One of the key instrument functions in any automated test equipment system, including a VXI system, are switches. Switches are used to route electrical signals in an automated test equipment system. For example, a power source may need to be sequentially applied to a series of test points. A switch instrument allows a single power source to connect to the first test point, then connect to the second test point, and finally break the connection to the first test point. The switch may continue in a like manner until all test points have been sequentially activated.
For an advanced automated test equipment system, typically several different types of switches are needed. For example, power switches are used for directing a power source within the test system. These power switches are configured to withstand typical test system voltages and higher current. Due to the high current requirements the power switches have fewer relay points per card. General purpose switch cards are designed for switching low level and low frequency signals that are less than two amps and operating at less than about 20 megahertz frequencies. However, even the general purpose switch cards are available in several configurations depending upon the particular need of the automated test system.
For example, general purpose cards are available having single pole single throw, single pole double throw, double pole single throw, or double pole double throw configurations. Further, various topologies are designed into switches depending upon the particular test application. A tree topology allows one input channel to selectively be applied to one of many output channels. A xe2x80x9cmultiplexerxe2x80x9d topology allows a single input to be connected to several outputs at one time, and a xe2x80x9cmatrixxe2x80x9d topology allows any of a multiple inputs to be selectively connected to any of a multiple of outputs. Thus, depending upon the current, frequencies, and other design considerations, various types of switches may be needed.
Indeed, it is typical for a VXI system to require two or more types of switches. Thereby a VXI test system integrator selects a first VXI switch card to solve a first switching need and then must select a second VXI card to solve the second switching need. Therefore, typical VXI configurations have several VXI chassis slots dedicated to switching. With VXI, efficiency and throughput is primarily gained through test density and conservation of space. It is therefore highly disadvantageous to use multiple VXI slots to accommodate multiple switching needs.
Therefore, a system integrator must choose between reducing the number of types of switch cards needed and use switch configurations that are less than optimal, or must use the optimal configuration of switch cards but sacrifice the slot space within the VXI chassis.
Ascor Incorporated, a Giga-Tronics company, has attempted to solve this problem by providing a multi slot VXI module with variable instruments cards. This multi slot VXI configuration has a chassis that accepts individual switch cards. This multi slot chassis fits into the standard VXI chassis. With Ascor, the smallest multi slot chassis completely occupies three slots in the VXI chassis. This three slot chassis can then accommodate up to six switch cards. Thereby, a system integrator choosing the Ascor switching system loses a minimum of three slots in the VXI chassis.
As test density is a high priority in selecting VXI instrumentation, several manufacturers provide multiple instruments configured into a single VXI card. For example, VXI Technology, Inc. offers a VXI modular instrumentation platform that hosts up to three instrumentation modules in a VXI slot card. However, each instrument placed in the VXI module instrumentation platform is a fully functioning VXI instrument. Thereby, each instrument has local intelligence on each module. Further, as the modular instrument platform is designed to accommodate instrumentation other than switches, any switch module is necessarily designed in a form factor not optimized for switch density.
Therefore, there exists a need in the VXI automated test environment for a switch system allowing greater flexibility in choosing switch types while maximizing the test density advantages in a VXI test system. Further there exists a need to modularize switch topologies and increase densities in a smaller footprint.
It is an object of the present invention to provide a VXI instrument card for providing switching services to an automated test equipment system. It is a further object of the invention that this VXI instrumentation card provides a scaleable configuration and also provides different types of switches in a single VXI card as required by particular test system requirements. It is a further object of the present invention that such configuration flexibility be provided in a single or double slot instrumentation card. It is also an object of the present invention to maximize the density of switch relays in a VXI instrument card.
Therefore, to overcome the disadvantages in the prior art and meet the objectives of the invention, a VXI modular switch instrument card is herein disclosed.
The modular switch instrument card has a single or double slot VXI bus card frame having a front panel. The card frame has module receiving areas for receiving selected switch modules. Each switch module is configured to provide a particular switching function. One or more switch modules may be positioned into the module receiving areas such that switch connectors on the switch modules extend through the front panel and are available for connection to an automated test system. The switch modules may be fixedly mounted within the card frame or may be removably coupled. Each switch module couples to an interconnect bus backplane enabling all installed switch modulars to communicate to a switch interface. The switch interface provides a communication interface to the VXI backplane, thereby providing a uniform and consistent programming interface independent of which switch modules are presently installed into the module receiving areas.
The above-disclosed modular switch instrumentation card allows a system integrator to modularly configure a single or double slot VXI instrument card to have the various switch types and topologies as required for a particular test system. Thereby a system integrator may select the switches optimum for a particular application while still dedicating only one or two slots of the VXI chassis to switching instrumentation. Such increased flexibility and density provides for increased test throughput and efficiencies.